1. Field of the Invention
The present invention relates to a method of and apparatus for manufacturing semiconductor packages, and more particularly, but not by way of limitation, to a mold assembly for manufacturing semiconductor packages which allows leadframes to be easily separated from a top mold section after a molding process.
2. History of Related Art
It is conventional in the electronic industry to encapsulate one or more semiconductor devices, such as integrated circuit chips, in a semiconductor package. These plastic packages protect a chip from environmental hazards, and provide means for electrically and mechanically attaching the chip to an intended device. Recently, such semiconductor packages have included metal leadframes for supporting an integrated circuit die which is bonded to a chip paddle region thereof Bond wires which electrically connect pads on the integrated circuit die to individual leads of the leadframe are then incorporated. A hard plastic encapsulant material which covers the bond wire, the integrated circuit die and other components, forms the exterior of the package. A primary focus in this design is to provide the die with adequate protection from the external environment in a reliable and effective manner.
As set forth above, the semiconductor package therein described incorporates a leadframe as the central supporting structure of such a package. A portion of the leadframe completely surrounded by the plastic encapsulant is internal to the package. Portions of the leadframe extend internally from the package and are used to connect the package externally. More information relative to leadframe technology may be found in Chapter 8 of the book Micro Electronics Packaging Handbook, (1989), edited by R. Tummula and E. Rymaszewski. This book is published by Van Nostrand Reinhold, 115 Fifth Avenue, New York, N.Y.
Once the integrated circuit dies or chips have been produced and encapsulated in a semiconductor package described above, they may be used in a variety of electronic appliances. A wide variety of electronic devices have been developed in recent years, such as cellular phones, portable computers, etc. Each of these devices typically includes a motherboard on which a significant number of such semiconductor packages are secured to, provide multiple electronic functions. These electronic appliances are themselves required to be reduced in size as consumer demand increases. Accordingly, not only are semiconductor chips highly integrated, but also semiconductor packages are miniaturized with a high increase of package mounting density.
According to such miniaturization tendency, semiconductor packages, which transmit electrical signals from semiconductor chips to motherboards and support the semiconductor chips on the motherboards, have been designed to have a size of about 1xc3x971 mm to 10xc3x9710 mm.
Aspects of the above-referenced manufacturing steps are set forth and shown in FIGS. 1 and 2, which are now referenced in combination. During the encapsulating step for constructing the semiconductor package as shown in FIG. 1, a plate-configuration bottom mold 10 is constructed with housing parts 12. The housing parts 12 are sunken to a predetermined depth from the upper surface 13 of the bottom mold 10 so as to allow the leadframe 30 (shown in FIG. 2) to be firmly placed thereon during encapsulation. The housing parts 12 are provided with a plurality of fixing pins 14 which are inserted into and fix the guide pinholes 29 formed in the leadframe 30 (shown in FIG. 2).
Still referring to FIG. 1, a top mold 20 is shown above bottom mold 10. The top mold 20 is also of a plate configuration, having a plurality of transports 22 which perforate the top mold 20 in the vertical direction. In the top mold 20, a runner 24 is grooved to a depth with a connection to each of the transports 22. Forming a tree-like configuration, a plurality of gates 26 are also grooved to a depth with connections to the runner 24. At the terminus of each of the gates 26 is formed a cavity 28 in which the package body 32 of the semiconductor package will be formed, as described in more detail below.
In operation, the bottom mold 10 and top mold 20 are used to encapsulate an assembled leadframe 30 placed therebetween. First, the leadframe 30 is safely placed on the housing parts 12 of the bottom mold 10. At this time, the guide pinholes 29 formed in the leadframe 30 are engaged with the fixing pins 14 formed in housing parts 12 to accurately fix the leadframe 30 (shown in FIG. 2). The top mold 20 is then clamped to the bottom mold 10. An amount of an encapsulation material is then introduced into the transports and pressurized with a transfer ram (not shown) to flow the encapsulation material through the runners 24 and the gates 26 into the cavities 28, described above.
Referring now to FIG. 2, following the filling of the encapsulation material between the bottom mold 10 and top mold 20 housing the leadframe 30, the top mold 20 is taken off, after which the leadframe 30 is removed out of the bottom mold 10 and subjected to the next process. In FIG. 2, there is shown the leadframe 30 after the encapsulation is completed on the bottom mold 10. It is conventional in the art to maintain the top mold 20 and the bottom mold 10 at such a predetermined temperature that the encapsulation material can smoothly flow through the runners 24 and the gates 26 to the cavities 28. After completion of the encapsulation, dregs of the encapsulation material which remain on the bottom mold 10 and the leadframe 30, that is, a transport curl 42, a runner curl 44 and a gate curl 46 are all removed.
After completion of the encapsulation, when the top mold is separated from the bottom mold, the leadframe frequently remains adhered to the top mold on account of the high adhesiveness of the encapsulation material. It is at this point that forcible secession by the hand of an operator can cause the breakage or bending of the leadframe. This aspect of the production process is a distinct disadvantage and is addressed by the present invention.
The present invention relates to a method of and apparatus for manufacturing semiconductor packages. More particularly, one aspect of the present invention includes a mold for manufacturing semiconductor packages, which allows leadframes to be easily separated from its top mold after a molding process. In another aspect, the present invention includes a mold for manufacturing semiconductor packages comprising a bottom mold having housing parts on the upper surface so as to allow leadframes to be placed in a flat state therein, and a top mold comprising transports perforating through the top mold in the vertical direction; runners formed at its lower surface with connections to the transports so as to introduce an encapsulation material into targets; a plurality of gates connected to the runner; and a volume of a cavity at the terminus of each of the gates, in which a package body is to be formed. A plurality of eject pins are mounted in the top mold for reciprocating into and out of the runners, thereby easily separating the leadframes from the top mold when the pins are actuated and move into the runners.
In a further aspect of the present invention, the above described invention includes eject pins formed at the intersections between the runners and the gates. Moreover, in the mold of the present invention, the runner curl which is most strongly stuck to the top mold can be pushed out downwardly by use of the eject pins so as to easily separate the leadframe from the top mold.
In yet another aspect of the present invention, a method of manufacturing a packaged semiconductor is presented. The method of making the packaged semiconductor includes the steps of providing a mold for manufacturing a packaged semiconductor upon a leadframe. The leadframe is of the type having a chip paddle formed therein and upon which a semiconductor chip is secured thereon. Input/output pads of the semiconductor chip are electrically connected to leads of the leadframe via wires. The semiconductor chip and leadframe assembly as above described are then secured within the mold. Encapsulant is then injected into the mold to form a semiconductor package body. The mold is separated, and the leadframes easily separated from the top mold portion after the molding process by the utilization of eject pins reciprocally mounted within the top mold in the grooved runner thereof for applying a uniform pressure across and easily separating the leadframe from the top mold.